Variable reluctance stepper motor

Abstract

A variable reluctance stepper motor including cooperating fixed and moving structures having tooth-like patterns of equal pitch but with the fixed and moving teeth having different lengths, measured in the direction of movement. The smaller teeth are divided into groups which are offset from one another by fractions of a tooth pitch to provide a bi-directional motor capable of being stepped from one position to the next with the teeth tending to produce force in the desired direction carrying essentially all of the flux and the teeth tending to produce force in the opposite direction carrying essentially no flux. Methods and techniques are also disclosed for fabricating tooth structures and bearing systems.

What I claim is: 
     
       1. A variable reluctance, bi-directional stepper motor comprising: a first member having a plurality of teeth, each of said teeth having both a pitch P and a width equal to P/2; and   a second member moveable relative to said first member, said second member comprising two poles, each pole having two sets of teeth, each of said teeth having both a pitch P and a width equal to P/4, the sets of teeth in each pole being offset from each other by an amount equal to (n±1/2)P, n being an integer, said poles being offset from each other by an amount equal to (m±1/4)P, m being an integer, each of said poles having associated therewith a winding adapted for connection to a direct current source, said second member having associated therewith at least one magnet.   
     
     
       2. A motor according to claim 1 wherein said first member is stationary and said second member moves. 
     
     
       3. A motor according to claim 1 wherein said second member is stationary and said first member moves. 
     
     
       4. A linear, variable reluctance, bi-directional stepper motor comprising: a first cylindrical member having a plurality of regular helical teeth with grooves therebetween, each of said teeth having both a pitch P and a width equal to P/2; and   a second cylindrical member surrounding at least a portion of said first member, said second member comprising two annular poles separated by an annular permanent magnet, each pole having two annular elements separated by an annular winding, adapted for connection to a direct current source, each element having a set of regular helical teeth with grooves therebetween, each of said teeth having both a pitch P and a width equal to P/4, the sets of teeth in each pole being offset longitudinally from each other by an amount equal to (n±1/2)P, n being an integer, said poles being offset from each other in the longitudinal direction by an amount equal to (m±1/4)P, m being an integer.   
     
     
       5. The motor according to claim 4 wherein said second element includes annular flux carrying members disposed on each side of said permanent magnet and between said permanent magnet and each pole, the cross section of said flux carrying members narrowing from said magnet toward each of said poles. 
     
     
       6. The motor according to claim 5 wherein said grooves of said elements are filled with a Teflon loaded material. 
     
     
       7. The motor according to claim 5 wherein said grooves of said elements are filled with a nylon loaded material. 
     
     
       8. The motor according to claim 5 wherein said second member further comprises a plurality of annular-shaped support bearings for supporting said second member on said first member. 
     
     
       9. The motor according to claim 8 wherein said first member includes a plated chromium coating thereon and said support bearings comprise oilite sintered bronze material. 
     
     
       10. The motor according to claim 8 wherein said first member includes a plated nickel coating thereon and said support bearings comprise treated aluminum impregnated with Teflon. 
     
     
       11. A disk, rotary, variable reluctance, bi-directional stepper motor comprising: a disk-shaped rotor mounted on a shaft and having a plurality of wedge-shaped, radially extending equally spaced teeth having an angular pitch P and an angular width equal to P/2; and   a stator comprising two poles one disposed on each side of said rotor, each stator pole having two sets of wedge-shaped, radially extending, equally spaced teeth having an angular pitch P and an angular width equal to P/4, the locii of said sets of stator teeth describing circles having two different radii, the sets of teeth in each stator pole being offset from each other by an angular amount equal to (n±1/2)P, n being an integer, the two stator poles being offset from each other by an angular amount equal to (m±1/4)P, m being an integer, each stator pole also including an annular magnet and an annular winding adapted for connection to a direct current source.   
     
     
       12. A motor according to claim 11 wherein said rotor further includes an annular-shaped iron ring disposed between said shaft and said rotor teeth to conduct flux between said stator poles. 
     
     
       13. A motor according to claim 13 wherein the magnet is a rare earth permanent magnet. 
     
     
       14. A cylindrical, rotary, variable bi-directional stepper motor comprising: a cylindrical rotor having a plurality of longitudinally extending teeth with grooves therebetween, said rotor teeth having an angular pitch P and an angular width equal to P/2; and   a cylindrical stator surrounding said rotor, said stator having two annular poles separated by an annular magnet, each stator pole having two sets of equally spaced, longitudinally extending teeth having an angular pitch P and an angular width equal to P/4, the sets of teeth in each stator pole being offset from each other by an angular amount equal to (n±1/2)P, n being an integer, the two stator poles being offset from each other by an angular amount equal to (m±1/4)P, m being an integer, the sets of teeth in each stator pole being separated by an annular winding adapted for connection to a direct current source.   
     
     
       15. The motor according to claim 14 wherein said magnet is a rare earth permanent magnet. 
     
     
       16. A variable reluctance, bi-directional stepper motor comprising: a first member having a plurality of teeth, each of said teething having both a pitch P and a width equal to P/2; and   a second member moveable relative to said first member, said second member comprising two poles, each pole having two sets of teeth, each of said teeth having both a pitch P and a width equal to P/4, the sets of teeth in each pole being offset from each other by an amount equal to (n±1/2)P, n being an integer, said poles being offset from each other by an amount equal to (m±1/4)P, m being an integer, each of said poles having associated therewith a winding adapted for connection to a direct current source, said second member having associated therewith at least one permanent magnet.